Process for producing acrylic fibers having excellent pilling resistance

ABSTRACT

Acrylic fibers having excellent pilling resistance are disclosed. The acrylic fibers have a plurality of elongated wedge shaped concave depressions extending into the fiber surface. The acrylic fibers are produced by pre-treating acrylic fibers with a modifier to modify the outer layer of individual fiber and then after-treating the fibers with an organic solvent for acrylic fiber.

United States Patent Orito et a1.

PROCESS FOR PRODUCING ACRYLIC FIBERS HAVING EXCELLENT PILLING RESISTANCEInventors: Zen-ichi Orito; Minoru Uchida;

Masatoshi Takesue; Hajime Sahara; Kihiro Flljii, all of Nagoya, JapanMitsubishi Rayon Co., Ltd., Tokyo, Japan Filed: Aug. 3, 1973 Appl. No.:385,290

Related US. Application Data Division of Ser. No. 146,148, May 24, 1971,Pat. No. 3,802,954.

Assignee:

Foreign Application Priority Data May 27, 1970 Japan 45-45502 June 5,1970 Japan..... 45-48614 June 8, 1970 Japan..... 45-49308 June 12, 1970Japan 45-50834 US. Cl. 264/344; 8/1 15.5; 8/130.1; 264/ 167; 264/ 182;264/343 Int. Cl. B29C 25/00; DO6M 3/26 Field of Search 264/210 F, 182,344, 343,

[ Dec. 23, 1975 [56] References Cited UNITED STATES PATENTS 2,590,4023/1952 Hall et a1. 8/115.5 2,889,611 6/1959 Bedell 8/115.5 3,124,4133/1964 Lowes...... 8/115.5 3,620,666 11/1971 Lenz et a1. 8/115.53,679,355 7/1972 Yamaguchi et a1 161/172 3,728,072 4/1973 Orito et a1.8/115.5 3,752,648 8/1973 Shichijo et al. 8/1 15.5

Primary Examiner-Jay H. Woo Attorney, Agent, or Firm-Armstrong, Nikaido& Wegner [5 7] ABSTRACT Acrylic fibers having excellent pillingresistance are disclosed. The acrylic fibers have a plurality ofelongated wedge shaped concave depressions extending into the fibersurface. The acrylic fibers are produced by pre-treating acrylic fiberswith a modifier to modify the outer layer of individual fiber and thenaftertreating the fibers with an organic solvent for acrylic fiber.

9 Claims, 5 Drawing Figures US. Patent Dec. 23, 1975 Sheet1of2 3,928,528

FIG

US Patent Dec. 23, 1975 She et20f2 3,928,528

PROCESS FOR PRODUCING ACRYLIC FIBERS HAVING EXCELLENT PILLING RESISTANCEThis is a division of application Ser. No. 146,148, filed May 24, 1971and now US. Pat. No. 3,802,954.

The present invention relates to acrylic fibers having a plurality ofelongated wedge shaped concave depressions extending into the fibersurface and process for producing the same.

The term fibers herein used includes the staple fibers, spun yarns, tow,knitted fabrics and woven fabrics.

Acrylic fibers have various excellent physical and chemical propertiesso that the fibers have been used in many fields including clothes.However, acrylic fibers have a defect that when the knitted or wovenfabrics made of acrylic fibers are worn for long time or just under anaction of rubbing such as washing, pills are formed on the surface ofthe fabrics. This phenomenon is well known as pilling and the pillsspoil the beautiful appearance of the fabrics. Therefore, prevention ofpilling has been earnestly desired.

Many attempts have been made to prevent or eliminate the formation ofpills on the surface of the fabrics.

For instance, such methods that particular conditions in fiber denier,fiber length and fiber cross section are used, or fibers are subjectedto a finishing treatment with a resin have been used. However,satisfactory results have never been attained by such methods.

Further, in order to produce acrylic fibers having particular hand, themethod has been used of making the fiber surface rough by embossing thefibers. However, the acrylic fibers obtained by this method have notbeen satisfactory from the point'of pilling resistance.

Accordingly, an object of the present invention is to provide acrylicfibers having excellent pilling resistance. 1

Another object of the present invention is to provide a processfor'producing acrylic fibers having excellent pilling resistance. a i IFurther objects of the present invention will be clear from thedescription that follows:

These objects of the present invention are achieved by pre-treatingacrylic fibers with a modifier to make the outer layer of individualfiber insoluble in dimethyl formamide at 100C. and then after-treatingthe acrylic fibers with an organic treating agent whereby a plurality ofelongated wedge shaped concave depressions extending into the fibersurface is formed.

According to the present invention, acrylic fibers having excellentpilling resistance as well as other excellent fiber properties can beproduced without losing the preferably fiber properties of acrylicfiber.

FIGS. 1, 2 and 3 are scanning electron microscopic photographs showingthe concave depressions formed into the surface of fibers. FIG. 4illustrates the method of measuring depth of the depression.

As is shown in the scanning electron microphotographs of FIGS. 1, 2 and3, the important characteristic of the fibers of the present inventionis that the fibers have a plurality of elongated wedge shaped concavedepressions extending into the surface thereof, the number of saiddepressions is more than 3 per inch along the length of an individualfiber and the elongated axis of said depressions is axially aligned inthe lengthwise direction of the fiber by which pilling resistance of thefiber is extremely improved.

The concave depressions shown in scanning electron microphotographs ofFIGS. 1 and 2 are somewhat different from the definite rhombic concavesshown in the photograph of FIG. 3 and this is due to the difference inspinning conditions. Therefore, the elongated wedge shaped concaves intothe surface of the fibers of the present invention include those havingthe shapes as shown in FIGS. 1 and 2 and those having the shape as shownin FIG. 3,

Acrylic fibers of the present invention have a plurality of elongatedwedge shaped concave depressions described hereinbefore.

The number of the concave depressions is preferably from 5 to 50 perinch along the length of an individual fiber. And the concavedepressions are preferably in rhombic shape. Length (a) of the majoraxis (elongated axis) of the individual depression is in the range of0.5 2 to 20p. and the maximum depth (b) of the concave depressions is inthe range of 0.2g. to 1011.. The major axis of the rhombic depressionsis aligned in the direction offthe fiber axis and the minor axis of therhombic depressions is aligned in the direction perpendicular to thefiber axis. 1

The major axis and depth of the elongated Wedge shaped concavedepressions in the fibers of the present invention are measured with ascanning electron microscope (.ISM Type II manufactured by JapanElectron Optics Laboratory Co., Ltd.). Depth of the concave depressionsis measured by taking photographs of the depression at two differentangles in the same field of vision and calculating the depth inaccordance with the following equation in reference to FIG. 4. FIG; 4(A)is a schematic view of the concave depression and FIG. 4(13) is aninclined schematic view of FIG. 4(A) at an angle of 0.

wherein b; Maximum depth of the elongated wedge shaped concavedepression. 1

p: Distance from the point 0 to the end point x of major axis. pf:Distance from the point 0 to the end point x of major axis afterinclination by 0.

6: Angle of inclination of sample fiber.

For taking said two photographs, a sample inclining apparatus(Goniometer specimen stage Type JSM-GS manufactured by Japan ElectronOptics Laboratory Co., Ltd.) is used with an angle of inclination of 20.

The fibers of the present invention are produced, for example, by thefollowing method.

In the present invention, acrylic fibers are produced from acrylonitrilehomopolymer, copolymer of acrylonitrile with at least one other monomercopolymerizable with acrylonitrile or their blend by the conventionalspinning methods. The acrylonitrile copolymer preferably contains morethan by weight of acrylonitrile and up to 20% by weight of at least oneother monomer copolymerizable with acrylonitrile.

The other monomer includes vinyl acetate, methyl acrylate, methylmethacrylate, ethyl acrylate, ethyl methacrylate, styrene, vinylchloride, vinylidene chloride, vinyl bromide, vinylidene bromide,acrylamide,

methacrylamide, methacrylonitrile, and monomers containing sulfoxylgroup or their salts.

Acrylic fibers thus obtained are pre-treated with a modifier to modifythe outer layer of individual fiber. By this treatment, the outer layerof individual fiber is made insoluble in dimethyl formamide at 100C, andthe pre-treatment is preferably carried out under such a condition thatmodified outer layer is 0.5 to 40% of the total cross sectional area ofan individual fiber.

Then, thus pre-treated acrylic fibers are after-treated with at leastone organic treating agent which is nonsolvent for the modified outerlayer, but is solvent for the un-modified inner layer of the acrylicfibers. Method of said after-treatment with the organic treating agentis as follows: (A) The pre-treated acrylic fibers are immersed in theorganic treating liquid and then washed with water and dried. (B) thepre-treated acrylic fibers are immersed in an aqueous organic treatingliquid, then squeezed and heat treated, or (C) the pre-treated acrylicfibers are treated with a vapor of the organic treating agent.

The pre-treatment may be carried out on the acrylic fibers in a form ofstaple, tow, spun yarn, knitted or woven fabric.

Acrylic fibers of the present invention may be mix spun with other kindof fibers. When the present acrylic fibers are mix spun with fiberswhich are degraded with the modifier to be used, it is preferable thatthe present acrylic fibers are pre-treated with the modifier, mix spunwith other kind of fibers and then after treated with the organictreating agent.

The cross sectional area of the modified outer layer is measured asfollows: the sample of the pre-treated fibers is embedded in monomericn-butyl methacrylate and heated to cause polymerization. A specimen ofthe cross section of the fibers is prepared by the same means as in thepreparation by optical microscope. Thereafter, the specimen is immersedin dimethyl formamide at 100C. to dissolve unmodified inner layer of thefiber and the modified outer layer which remained insoluble isphotographed with a scanning electron microscope. The sectional area iscalculated from the photograph.

The modifiers to be used for the pre-treatment include, for example,saponifying agents such as alkali metal hydroxides such as sodiumhydroxide, potassium hydroxide, lithium hydroxide, and sulfuric acid andchemical reacting agents such as hydroxylamine sulfate, andhydroxylamine phosphate.

The modification treatment is carried out so that area of the modifiedouter layer is 0.5 to 40% of cross sectional area of an individualacrylic fibers. However, actual conditions vary depending upon the kindof the modifiers, size of fibers, etc. Therefore, suitable modificationtreatment may be carried out within the scope of the present invention.

Preferable organic treating agents for producing acrylic fibers of thepresent invention are as follows:

i. Amide compounds dimethyl formamide, di-

methyl acetamide ii. Sulfon and sulfoxide compounds dimethyl sulfoxide,dimethyl sulfon iii. Carbonate compounds ethylene carbonate iv. Nitrilecompounds malononitrile, adiponitrile,

acetonitrile These organic treating agents may be used singly or jointlyin the form of 100% solution or dilute solution. Furthermore, an inertviscosity increasing agent such as ethylene glycol or glycerine may beadded thereto.

Embodiments of the after-treating methods with these organic treatingagents are as follows:

A. In the method where fibers are immersed in the treating agent, thepre-treated acrylic fibers are immersed in a solution of the organictreating agent. The concentration of the solution is higher thantreating temperature is 10 to C. and treating time is 2 minutes to 1hour. In this embodiment, a mixture such as dimethyl formamide-ethylenecarbonate, dimethyl acetamide-ethylene carbonate may be used.

B. In the method where fibers are immersed in the organic agent,squeezed and then heat treated, the pretreated fibers are immersed in anaqueous solution of the organic treating agent. Representative examplesof the agents include dimethyl formamide, dimethyl acetamide, dimethylsulfoxide and ethylene carbonate. These organic treating agents may bepreferably used in such a manner that amount of the agent adhered to thefibers immediately after squeezing is more than 15%, more preferably 15to 100% of the weight of the dried fiber. The heat treating temperatureis preferably 50 to C. As to the concentration of the aqueous solution,heating temperature and heating time, there is no special limitation.

C. In the method where fibers are treated with a vapour of the organicagent, the pre-treated fibers are exposed in a vapour of organicsolvents for acrylic fibers having a boiling point of lower than 250C.

As the solvents for acrylic fibers, inorganic solvents may be usedbeside the organic solvents. However, the organic solvents such asdimethyl formamide, dimethyl acetamide and dimethyl sulfoxide are themost preferably used. When the pre-treated fibers are after-treated withinorganic solvents, the fibers themselves are swollen or dissolved tocause adhesion between the fibers. Furthermore, inorganic solvents arevapourized with difficulty.

It is difficult to give a clear explanation of the mechanism offormation of the concave depressions extending into the fiber surface bytreating the pre-treated acrylic fibers with the organic treating agent.However,

it is considered that the concave depressions are formed due toextraction of the unmodified inner layer (soluble in dimethyl formamide)through the modified outer layer (insoluble in dimethyl formamide) bythe treatment with the organic treating agent.

In the knitted or woven fabrics of the acrylic fibers of the presentinvention, the fibers have particular concave depressions, which provideweak points in strength of the fibers to cause easy falling off ofpills. As a result, prevention of pilling can be accomplished.

Furthermore, the concave depressions of the fibers of the presentinvention have an elongated wedge shape and the major axis of thedepressions is aligned in the lengthwise direction of the fiber axis andthe minor axis of the depression is aligned in the directionperpendicular to the fiber axis. Said concave depressions extend intothe surface of the fibers and are dispersed in the whole surface of thefibers. Therefore, contact area between single fibers is decreased andthus the knitted or woven fabrics have soft hand and excellent shapestability.

The present invention will be illustrated by the Examples.

EXAMPLE I A polymer comprising 93% by weight of acrylonitrile and 7% byweight of vinyl acetate was spun by the conventional wet spinning methodto obtain a tow having monofilamentary denier of 3 andtotal denier of480,000. The tow was cut by the turbo stapler to obtain slivers (highbulk fibers). A part of said slivers were shrunk by a fiber setter toobtain regular fibers. Forty parts of the high bulk fibers and 60 partsof the regular fibers were worsted-spun to obtain high bulk two foldedyarns (250/360 T/M) of 36 metric counts. Said high bulk yarns werepre-treated with 0.5% aqueous solution of sodium hydroxide at 90C. for30 minutes, then bleached with 1% aqueous solution of acetic acid at98C. for 15 minutes, washed with water and dried. The fibers wereinsoluble in dimethyl formamide at iO0C. Said insolubilized portion was7% of total cross sectional area of the fiber.

Thus treated yarns were immersed at a liquid ratio of l 50 in thetreating agents as shown in Table A to form concave depression havingcharacteristics shown in Table A.

As one example, microphotograph of the fibers treated with treatingagent l in Table A by a scanning electron microscope is shown in FIG. 1.

pre-treated with 2% aqueous solution of sodium hydroxide at 90C for 30minutes, washed with water and dried.

A part of the pre-treated fibers were embedded in monomeric n-butylmethacrylate and heated to effect polymerization. Thereafter, a specimenof cross section of the fibers having a thickness of about 5 p wasprepared. This specimen was immersed in dimethylformamide kept at 100C.to cause partial dissolution thereof. By this procedure, it wasacknowledged that undissolved part was the outer layer of the fibers andthe area of this outer layer was 21% of total cross sectional area.

The pre-treated fibers were immersed in dimethylformamide at 25C. for 5minutes. Then, solvent was removed by washing with water and dried.Elongated wedge-shaped concave depressions, most of which were rhombicin shape, were intermittently formed extending into the surface of thefibers. The shapes of the concaves are shown in Table C. As referentialExample, non-pretreated fibers were immersed in dimethylformamide at25C. to cause dissolution of the fibers.

Table A I Concen- Tempera- Immersion Major axis Maximum depth Number ofTreating agent tration ture time (a) o (b) of depression (70) ("C)(min.) depression 1.) depression 1) inch Dimethylformamide 98 25 5 120.5 2 40 Dimethylformamide 50/50 20 4 10 0.5 2 25 Ethylene carbonateEthylene carbonate 90/i0 28 20 3 8 0.4 2 20 Water Dimethylacetamide 9825 20 S l2 0 5 2 Acetonitrile 98 20 2 8 0.5 2 l8 EXAMPLE 2 Table C IMajor axis (a) of Depth (b) of Number of The high bulk yarns produced bythe same method as Fi rs depressi n (a) depression depression in Example1 were pre-treated with aqueous solution of the modifiers shown in TableB to make the outer layer This Example 3 10 0.3 l 12 of the fibersinsoluble in'dimethylformamide at 100C. ggzg' o o 0 Ratio of area of theouter layer to that oftotal sectional area of the fibers is also shownin Table B.

. Then, thus treated yams were immersed in 100% dimethylformamide at 25Cfor 20 minutes to obtain the fibers having concave depressions shown inTable B.

Table B Concen- Treating Area of Meier axis Maximum depth Number ofTreating tration Temperature time outer layer (a) of (b) of depressionagent (10 (C) (min) depression (a) deprelslon (u) inch Sodium 1.5 30 i53 8 0.5 L5 19 hydroxide 0.5 90 30 7 5 12 0.5 2.0 40 Potassium 3.0 95 30i3 3 9 0.5 1.5 20 hydroxide I Sodium 1.5 95 30 i4 3 10 0.5 L5 20hydroxide I Sulfuric 60.0 25 i5 18 1.0 5 0.3 0.8 l7

acid

EXAMPLE 3 obtained in this Example is shown in FIG. 3.

A copolymer of 93% by weight of aerylonitrile and 7% by weight of vinylacetate was spun by the conventional dryspinning methodto obtain staplefibers (3 deniers per filament'serni dull). The staple fibers wereEXAMPLE 4 30 minutes, and then bleached with 1% aqueous solution ofacetic acid at 98C. for minutes, washed with water and dried. The outerlayer of the fibers was insoluble in dimethylformamide at 100C. and thisinsolubilized part was 21% of total cross sectional area of the fibers.

Thus pre-treated high bulk yarns were immersed in 30% aqueous solutionof dimethyiformamide kept at C. and then squeezed in such a manner thatthe amount of dimethyiformamide solution adhered tothe yarns was 70% ofweight of dried fibers. Then, the yarns were heat treated for one hourin a drier kept at 90C. Said yarns were dyed and subjected to softeningtreatment and then were made into a sweater by 140 Full Fashion knittingmachine. M

In the surface of the fibers, elongated wedge-shaped concave depressionswere formed. The concave depressions have a length of major axis of 1.2to 7 p. and a depth of 0.4 to l p. and number depressions per 1 inch was15.

Said knitted fabric was tested by Random tumble type pilling tester andthe results thereof are shown in Table D. It is clear from the Table Dthat the knitted fabric obtained in this Example had conspicuouslyexcellent pilling resistance.

Table D comparatively shows the test results on a knitted fabricobtained from conventional acrylic fibers. i

Table D Fabric Piiiing resistance (grade) Fabric of this Example 5Fabric of conventional acrylic fibers 2 3 Grade of pilling resistancewas decided by surface changes resulted after operation of randomsu'mpic type tester for minutes in accordance with JiS'. L-ltilii- 5thgrade No formation of pills and no change of surface A few pills andchanges Medium number of pills and changes Many pills and changesExtremely many pills and changes 4th grade 3rd grade 2nd grade lst gradeFurthermore, the knittedfabric obtained in this Example had soft handand completely maintained excellent properties of acrylic fibers.

EXAMPLE 5 36 counts (metric count) two folded yarns. The yarns wereimmersed in aqueous solutions of the'treating agents in Table E and weresqueezed in such a manner that the'amount of the solution adhered to thefibers was of weight of the dried fibers. Thereafter, the yarns wereheat treated for l hour in a drier kept at C.

The states of the acrylic fibers in the yarns obtained are shown inTable E.

Acrylic fibers (3 dealers per filament) were pretreated with 2% aqueoussoiution'of sodium hydroxide at 90C. for 30 minutes and then bleachedwith 2% aqueous solution of oxalic acid at 98C. for 15 minutes. Theouter layer of the fibers thus pro-treated was insoluble indimethylformamide at 100C. and this outer layer was-21% of total crosssectional area of the fibers.

Said fibers were spun into two folded yarns (185/320 T/M) of 36 metriccounts, which were exposed to saturated vapor of dimethylformamide at100C. for 5 minutes, washed with water and dried. Thus treated yarnswere dyed and subjected tosoftening-treatment and then made into knittedfabric. in the fiber surface of this knitted fabric, elongatedwedge-shaped concave depressions having a major axis of L341. to 5p. anda depth of 0.4 a to 0.8 a were formed. Numberof the depressions was20/inch.

Said knitted fabric had an excellent pilling resistance as shown inTable F.

. Table F Filling resistance Knitted fabric of this Example ,5th gradeEXAMPLE 7 Acrylic fiber two folded spun yarns (250/360 TIM) of 32 metriccounts were immersed in a mixed aqueous solution of 10% of glycerine and10% sulfuric acid, and then squeezed. Thereafter, the yarns were heatedat C. for 10 minutes to pre=treat the yearns, washed with water anddried. The outer layer of the fibers was Table G Vapor Length (a) ofAfter treating temperature major axis of Maximum depth (b) Number ofdepression/inch agent ("C) depression (,u.) of depression (a)Dimethylformamide I 1.2 6 0.5 L 19 Dimethylsulfoxide 120 L0 8 0.5 1.5 20Acetonitrile 8O [.4 10 0.4 L0 19 What is claimed is: r

l. A process for producing acrylic fibers having a plurality ofelongated wedge shaped concave depressions extending into the surfacethereof, the number of said depressions being more than 3 per inch alongthe length of an individual fiber and the elongated axis of saiddepressions being axially aligned in the lengthwise direction of thefiber, which comprises 'pre-treating acrylic fibers with a modifierselected from the group consisting of alkali metal hydroxides, sulfuricacid and hydroxylamine salts to modify the outer portion of individualfiber to make the outer portion of individual fiber insoluble indimethyl formamide at 100C. and then after-treating the fibers with anorganic treating agent which is non-solvent for the modifiedouterportion, but is solvent for the unmodified inner portion of theacrylic fibers and which is selected from the group consisting ofdimethyl formamide, dimethyl acetamide, dimethyl su1fon,-dimethylsulfoxide, ethylene carbonate, acetonitrile, malonitrile andadiponitrile.

2. A process according to claim 1, wherein said acrylic fibers arepre-treatedwith said modifier, and then immersed in an 85100% solutionof said organic treating agent at a temperature of lO100C.

3. A process according to claim 1, wherein said acrylic fibers arepretreated with said modifier, and

then immersed in a 30-IOO% solution of said organic treating agent,squeezed and then heat treated at a temperature of from l20C.

4. .A process according t0 claim 1, wherein said acrylic fibers arepre-treated with said modifier and then treated withv a vapour of saidorganic treating agent. r

5. A process according to claim 1, wherein said organic treating agentis selected from the group consisting of a mixture of dimethyl formamideand ethylene carbonate and a mixture of dimethyl acetamide and ethylenecarbonate.

6. A process according to claim 3, wherein the amount of said organictreating agent adhered to the fibers immediately after said squeezing ismore than 15% of the weight of dried fiber.

7. A process according to claim 6, wherein the amount of said organictreating agent adhered to the fibers immediately after said squeezing is15-100% of the weight of dried fiber.

8. The process of claim 2 wherein said solution of organic treatingagent is an aqueous solution.

9. The. process of claim 3 wherein said solution of organic treatingagent is an aqueous solution.

1. A PROCESS FOR PRODUCING ACRYLIC FIBERS HAVING A PLURALITY OFELONGATED WEDGE SHAPED ONCAVE DEPRESSIONS EXTENDING INTO THE SURFACETHEREOF, THE NUMBER OF SAID DEPRESSIONS BEING MORE THAN 3 PER INCH ALONGTHE LENGTH OF AN INDIVIDUAL FIBER AND THE ELONGATED AXIS OF SAIDDEPRESSIONS BEING AXIALLY ALIGNED IN THE LENGTHWISE DIRECTION OF THEFIBER, WHICH COMPRISES PRETREATING ACRYLIC FIBERS WITH A MODIFIERSELECTED FROM THE GROUP CONSISTING OF ALKALI METAL HYDROXIDES, SULFURICACID AND HYDROXYLAMINE SALTS TO MODIFY THE OUTER PORTION OF INDIVIDUALFIBER TO MAKE THE OUTER PORTION OF INDIVIDUAL FIBER INSOLUBLE INDIMETHYL FORMAMIDE AT 100*C. AND THEN AFTER-TREATING THE FIBER TO WITHAN ORGANIC TREATING AGENT WHICH IS NON-SOLVENT FOR THE MODIFIED OUTERPORTION, BUT IS SOLVENT FOR THE UNMODIFIED INNER PORTION OF THE ACRYLICFIBERS AND WHICH IS SELECTED FROM THE GROUP CONSISTING OF DIMETHYLFORMAMIDE, DIMETHYL ACETAMIDE, DIMETHYL SULFON, DIMETHYL SULFOXIDE,ETHYLENE CARBONATE, ACETONITRILE, MALONITRILE AND ADIPONITRILE.
 2. Aprocess according to claim 1, wherein said acrylic fibers arepre-treated with said modifier, and then immersed in aN 85-100% solutionof said organic treating agent at a temperature of 10*-100*C.
 3. Aprocess according to claim 1, wherein said acrylic fibers arepre-treated with said modifier, and then immersed in a 30-100% solutionof said organic treating agent, squeezed and then heat treated at atemperature of from 50*-120*C.
 4. A process according to claim 1,wherein said acrylic fibers are pre-treated with said modifier and thentreated with a vapour of said organic treating agent.
 5. A processaccording to claim 1, wherein said organic treating agent is selectedfrom the group consisting of a mixture of dimethyl formamide andethylene carbonate and a mixture of dimethyl acetamide and ethylenecarbonate.
 6. A process according to claim 3, wherein the amount of saidorganic treating agent adhered to the fibers immediately after saidsqueezing is more than 15% of the weight of dried fiber.
 7. A processaccording to claim 6, wherein the amount of said organic treating agentadhered to the fibers immediately after said squeezing is 15-100% of theweight of dried fiber.
 8. The process of claim 2 wherein said solutionof organic treating agent is an aqueous solution.
 9. The process ofclaim 3 wherein said solution of organic treating agent is an aqueoussolution.